ESS 101 B Lab 5 Quiz: Sedimentary Rocks
Questions and Answers 2025/2026
Solved 100% Correct
PART 1: WEATHERING & SEDIMENT FORMATION
Q1. What are the three categories of sedimentary rocks based on their
composition and mode of formation?
A) Igneous, metamorphic, and volcanic
B) Clastic (detrital), chemical/biochemical, and organic
C) Limestone, sandstone, and shale
D) Felsic, intermediate, and mafic
Correct ,,,,answer,,,: B
Rationale: Sedimentary rocks are divided into three categories depending
on what type of sediment(s) they are made of: (1) Clastic (or detrital),
composed of clasts (broken pieces) of other rocks; (2) Chemical and
biochemical, formed by the precipitation of ions; and (3) Organic,
composed of organic materials .
Q2. Which type of weathering physically breaks rock into smaller
pieces without changing its chemical composition?
A) Chemical weathering
B) Mechanical (physical) weathering
,C) Biological weathering
D) Oxidation
Correct ,,,,answer,,,: B
Rationale: Mechanical weathering (also called physical weathering) is
when rock physically breaks into smaller pieces. Processes include frost
wedging, abrasion, and exfoliation. Chemical weathering involves
chemical reactions that alter or dissolve minerals .
Q3. What type of weathering transforms existing minerals into new
minerals and releases ions into the environment?
A) Mechanical weathering
B) Physical weathering
C) Chemical weathering
D) Thermal weathering
Correct ,,,,answer,,,: C
Rationale: Chemical weathering transforms existing minerals into new
minerals and releases ions into the environment through reactions such
as hydrolysis, oxidation, and dissolution. For example, hydrolysis turns
plagioclase into kaolinite clay .
Q4. According to Bowen's Reaction Series, which mineral is most
stable (least reactive) at the Earth's surface?
A) Olivine
B) Pyroxene
C) Biotite
D) Orthoclase (quartz)
Correct ,,,,answer,,,: D
Rationale: The closer the conditions of formation are to conditions at the
Earth's surface, the more stable the mineral. Quartz and orthoclase (felsic
,minerals) form at lower temperatures and are more stable at the surface.
Mafic minerals (olivine, pyroxene) are unstable and weather quickly .
Q5. Which mineral is most resistant to chemical weathering and
commonly found as sand grains in beaches and deserts?
A) Calcite
B) Feldspar
C) Quartz
D) Mica
Correct ,,,,answer,,,: C
Rationale: Quartz is abundant, durable, and chemically stable at the
Earth's surface. It is highly resistant to chemical weathering, which is why
it dominates clastic sedimentary rocks like sandstone .
Q6. The process of converting loose sediment into solid sedimentary
rock is called:
A) Weathering
B) Erosion
C) Lithification
D) Metamorphism
Correct ,,,,answer,,,: C
Rationale: Lithification is the process that converts loose sediment into
solid rock. It includes compaction (squeezing of grains) and cementation
(precipitation of minerals between grains) .
Q7. What are the two main processes involved in lithification?
A) Melting and cooling
B) Compaction and cementation
C) Heat and pressure
D) Weathering and erosion
, Correct ,,,,answer,,,: B
Rationale: Lithification involves compaction (reducing pore space by the
weight of overlying sediment) and cementation (minerals like calcite or
quartz precipitate between grains, binding them together) .
Q8. Loose, solid particles that originate from weathering of pre-existing
rocks, precipitation from solution, or remains of organisms are called:
A) Magma
B) Sediment
C) Crystals
D) Fossils
Correct ,,,,answer,,,: B
*Rationale: Sediment consists of loose, solid particles originating from (1)
weathering and erosion of pre-existing rocks, (2) chemical precipitation
from solution, or (3) the remains or traces of once-living organisms .*
Q9. In the hydrolysis reaction that weathers plagioclase feldspar into
kaolinite, what ion is released into surface waters?
A) Silica (SiO₂)
B) Aluminum (Al³⁺)
C) Calcium (Ca²⁺)
D) Iron (Fe²⁺)
Correct ,,,,answer,,,: C
Rationale: The hydrolysis reaction CaAl₂Si₂O₈ + H₂CO₃ + ½O₂ →
Al₂Si₂O₅(OH)₄ + Ca²⁺ + CO₃²⁻ turns plagioclase into kaolinite clay. The
leftover calcium from plagioclase enters surface waters as a Ca²⁺ ion .
Q10. Which type of weathering is primarily responsible for forming the
rounded shapes of rocks in a riverbed?
A) Frost wedging
B) Abrasion (mechanical weathering)
Questions and Answers 2025/2026
Solved 100% Correct
PART 1: WEATHERING & SEDIMENT FORMATION
Q1. What are the three categories of sedimentary rocks based on their
composition and mode of formation?
A) Igneous, metamorphic, and volcanic
B) Clastic (detrital), chemical/biochemical, and organic
C) Limestone, sandstone, and shale
D) Felsic, intermediate, and mafic
Correct ,,,,answer,,,: B
Rationale: Sedimentary rocks are divided into three categories depending
on what type of sediment(s) they are made of: (1) Clastic (or detrital),
composed of clasts (broken pieces) of other rocks; (2) Chemical and
biochemical, formed by the precipitation of ions; and (3) Organic,
composed of organic materials .
Q2. Which type of weathering physically breaks rock into smaller
pieces without changing its chemical composition?
A) Chemical weathering
B) Mechanical (physical) weathering
,C) Biological weathering
D) Oxidation
Correct ,,,,answer,,,: B
Rationale: Mechanical weathering (also called physical weathering) is
when rock physically breaks into smaller pieces. Processes include frost
wedging, abrasion, and exfoliation. Chemical weathering involves
chemical reactions that alter or dissolve minerals .
Q3. What type of weathering transforms existing minerals into new
minerals and releases ions into the environment?
A) Mechanical weathering
B) Physical weathering
C) Chemical weathering
D) Thermal weathering
Correct ,,,,answer,,,: C
Rationale: Chemical weathering transforms existing minerals into new
minerals and releases ions into the environment through reactions such
as hydrolysis, oxidation, and dissolution. For example, hydrolysis turns
plagioclase into kaolinite clay .
Q4. According to Bowen's Reaction Series, which mineral is most
stable (least reactive) at the Earth's surface?
A) Olivine
B) Pyroxene
C) Biotite
D) Orthoclase (quartz)
Correct ,,,,answer,,,: D
Rationale: The closer the conditions of formation are to conditions at the
Earth's surface, the more stable the mineral. Quartz and orthoclase (felsic
,minerals) form at lower temperatures and are more stable at the surface.
Mafic minerals (olivine, pyroxene) are unstable and weather quickly .
Q5. Which mineral is most resistant to chemical weathering and
commonly found as sand grains in beaches and deserts?
A) Calcite
B) Feldspar
C) Quartz
D) Mica
Correct ,,,,answer,,,: C
Rationale: Quartz is abundant, durable, and chemically stable at the
Earth's surface. It is highly resistant to chemical weathering, which is why
it dominates clastic sedimentary rocks like sandstone .
Q6. The process of converting loose sediment into solid sedimentary
rock is called:
A) Weathering
B) Erosion
C) Lithification
D) Metamorphism
Correct ,,,,answer,,,: C
Rationale: Lithification is the process that converts loose sediment into
solid rock. It includes compaction (squeezing of grains) and cementation
(precipitation of minerals between grains) .
Q7. What are the two main processes involved in lithification?
A) Melting and cooling
B) Compaction and cementation
C) Heat and pressure
D) Weathering and erosion
, Correct ,,,,answer,,,: B
Rationale: Lithification involves compaction (reducing pore space by the
weight of overlying sediment) and cementation (minerals like calcite or
quartz precipitate between grains, binding them together) .
Q8. Loose, solid particles that originate from weathering of pre-existing
rocks, precipitation from solution, or remains of organisms are called:
A) Magma
B) Sediment
C) Crystals
D) Fossils
Correct ,,,,answer,,,: B
*Rationale: Sediment consists of loose, solid particles originating from (1)
weathering and erosion of pre-existing rocks, (2) chemical precipitation
from solution, or (3) the remains or traces of once-living organisms .*
Q9. In the hydrolysis reaction that weathers plagioclase feldspar into
kaolinite, what ion is released into surface waters?
A) Silica (SiO₂)
B) Aluminum (Al³⁺)
C) Calcium (Ca²⁺)
D) Iron (Fe²⁺)
Correct ,,,,answer,,,: C
Rationale: The hydrolysis reaction CaAl₂Si₂O₈ + H₂CO₃ + ½O₂ →
Al₂Si₂O₅(OH)₄ + Ca²⁺ + CO₃²⁻ turns plagioclase into kaolinite clay. The
leftover calcium from plagioclase enters surface waters as a Ca²⁺ ion .
Q10. Which type of weathering is primarily responsible for forming the
rounded shapes of rocks in a riverbed?
A) Frost wedging
B) Abrasion (mechanical weathering)
